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Abstract:

A large format digital camera has a primary camera system configured for
collecting panchromatic image data and a secondary camera system
configured for collecting color image data. The secondary camera system
has an optical system that has a longer focal length than the optical
system of the primary camera system. The resolution of the secondary
camera system is greater than the resolution of the primary camera
system. The footprint of images produced by the primary camera system is
larger in size than the footprint of images produced by the secondary
camera system. Images produced by the primary camera system offer
information for performing image-based georeferencing by means of
photogrammetric triangulation. Images produced by the secondary camera
system offer a high-resolution narrow angle color image suitable for use
in ortho image production.

Claims:

1. A large format framing camera, comprising: a first camera system
configured for collecting panchromatic image data, the first camera
system comprising a first optical system having a first focal length; and
a second camera system configured for collecting color image data, the
second camera system comprising a second optical system having a second
focal length, and wherein the second focal length is longer than the
first focal length.

2. The large format camera of claim 1, wherein the first camera system
further comprises an electro optical detector array having a first
resolution for collecting the panchromatic image data, wherein the second
camera system further comprises an electro optical detector array having
a second resolution for collecting the color image data, and wherein the
second resolution is greater than the first resolution.

3. The large format camera of claim 2, wherein the first camera system
has a first footprint, wherein the second camera system has a second
footprint, and wherein the second footprint is smaller than the first
footprint.

4. The large format camera of claim 3, wherein the second footprint
covers a center of the first footprint.

5. The large format camera of claim 4, wherein the large format camera is
configured to output a first image comprising the panchromatic image data
and a second image comprising the color image data.

6. The apparatus of claim 5, wherein a radiometric resolution of the
second camera system is greater than the radiometric resolution of the
first camera system.

7. The large format camera of claim 6, wherein the first camera system
and the second camera system are mounted within a single housing.

8. The large format camera of claim 7, wherein the first camera system
and the second camera system are configured to generate a sequence of
consecutive first and second images, wherein consecutive first images
overlap one another, consecutive second images overlap one another, and
wherein the overlap of the first images is greater than the overlap of
the second images.

9. The large format camera of claim 8, wherein the first images are
suitable for use in a photogrammetric workflow that includes image-based
georeferencing and digital surface modeling.

10. The large format camera of claim 9, wherein the second images are
suitable for use in a photogrammetric workflow that includes ortho image
production.

11. A large format framing camera, comprising: a first camera system
configured for collecting panchromatic image data, the first camera
system comprising a first optical system having a first focal length and
being configured output a first image comprising the panchromatic image
data, the first image having a first footprint; and a second camera
system configured for collecting color image data, the second camera
system comprising a second optical system having a second focal length
and being configured to output a second image comprising the color image
data, the second image having a second footprint, and wherein the second
focal length is longer than the first focal length and the second
footprint is smaller than the first footprint.

12. The large format camera of claim 11, wherein the second footprint
covers a center of the first footprint.

13. The large format camera of claim 12, wherein the first camera system
and the second camera system are mounted within a single housing.

14. The large format camera of claim 13, wherein the first camera system
further comprises an electro optical detector array having a first
resolution for collecting the panchromatic image data, wherein the second
camera system further comprises an electro optical detector array having
a second resolution for collecting the color image data, and wherein the
second resolution is greater than the first resolution.

15. The large format camera of claim 14, wherein the first camera system
and the second camera system are configured to generate a sequence of
consecutive first and second images, wherein consecutive first images
overlap one another, consecutive second images overlap one another, and
wherein the overlap of the first images is greater than the overlap of
the second images.

16. A large format framing camera, comprising: a housing; a first camera
system mounted within the housing and configured for collecting
panchromatic image data, the first camera system comprising a first
optical system having a first focal length and an electro optical
detector array having a first resolution for collecting the panchromatic
image data; and a second camera system mounted within the housing
configured for collecting color image data, the second camera system
comprising a second optical system having a second focal length and an
electro optical detector array having a second resolution for collecting
the color image data, and wherein the second focal length is longer than
the first focal length and the second resolution is greater than the
first resolution.

17. The large format camera of claim 16, wherein the first camera system
has a first footprint, wherein the second camera system has a second
footprint, wherein the second footprint is smaller than the first
footprint, and wherein the second footprint covers a center of the first
footprint.

18. The large format camera of claim 17, wherein the large format camera
is configured to output a first image comprising the panchromatic image
data and a second image comprising the color image data.

19. The large format camera of claim 18, wherein the first camera system
is configured to generate a consecutive sequence of first images and the
second camera system is configured to generate a consecutive sequence of
second images, wherein consecutive first images overlap one another,
consecutive second images overlap one another, and wherein the overlap of
the first images is greater than the overlap of the second images.

20. The large format camera of claim 19, wherein the first images are
suitable for use in a photogrammetric workflow that includes image-based
georeferencing and digital surface modeling and wherein the second images
are suitable for ortho image production.

Description:

BACKGROUND

[0001] Traditional methods and camera systems utilized for the optical
airborne registration (photogrammetric mapping) of urban areas have
typically suffered from several problems. For instance, the aviation
regulations near urban airports typically do not allow aircraft to fly at
altitudes low enough for achieving acceptable image scales using
conventional camera systems. As another example, images generated by
conventional airborne camera systems typically suffer from perspective
foreshortening, which causes buildings to appear as if they are leaning.
This is particularly problematic in urban areas that often have many tall
buildings.

[0002] It is with respect to these and other considerations that the
disclosure made herein is presented.

SUMMARY

[0003] Concepts and technologies are described herein for a large format
digital camera having multiple optical systems and detector arrays.
Through an implementation of the concepts and technologies presented
herein, a large format digital camera having multiple optical systems and
detector arrays is provided that is suitable for use in the airborne
optical registration of urban areas. In particular, a large format
digital camera is disclosed herein that is capable of producing images at
different photographic scales. The large format digital camera presented
herein can produce panchromatic images using a wide-angle geometry that
are suitable for use in a photogrammetric workflow that includes
image-based georeferencing and digital surface modeling. The large format
digital camera disclosed herein can also produce color images using a
narrow-angle geometry suitable for use in a photogrammetric workflow that
includes ortho image production. An ortho image is an image that shows
ground objects in an orthographic projection.

[0004] According to one aspect presented herein, a large format camera is
provided that includes a primary camera system, which may be referred to
herein as the "first camera system," and a secondary camera system, which
may be referred to herein as the "second camera system." The primary
camera system is configured for collecting panchromatic image data and
the secondary camera system is configured for collecting color image
data. The secondary camera system has an optical system that has a longer
focal length than the optical system of the primary camera system. The
primary camera system and the secondary camera system may be mounted
within a common housing suitable for installation and use within an
aircraft.

[0005] According to other aspects, the primary camera system has an
electro optical detector array capable of capturing the panchromatic
image data. The secondary camera system has an electro optical detector
array capable of capturing the color image data. The resolution of the
electro optical detector in the secondary camera system is greater than
the resolution of the electro optical detector in the primary camera
system. According to other aspects, the radiometric resolution of the
secondary camera system may be greater than the radiometric resolution of
the primary camera system.

[0006] According to other aspects, the primary camera system and the
secondary camera system are configured such that the large format digital
camera can produce images at two different image scales offering two
different footprints. Images produced by the primary camera system have a
larger footprint and are larger in size than those produced by the
secondary camera system and offer information for performing image-based
georeferencing by means of photogrammetric triangulation. Images produced
by the secondary camera system have a smaller footprint and are smaller
in size than those produced by the primary camera system and offer a
high-resolution narrow angle color image. The color images produced by
the secondary camera system may be utilized as a source data set for
high-resolution ortho image production. The footprint of the secondary
camera system may be configured to cover the center of the footprint of
the primary camera system.

[0007] According to other aspects, the large format digital camera may be
configured to generate a sequence of consecutive images along a flight
line. The large format camera may be further configured such that the
primary camera system produces a sequence of consecutive panchromatic
images that overlap one another. The secondary camera system may be
configured to produce a sequence of consecutive color images that overlap
one another and the images produced by the primary camera system. The
overlap between consecutive panchromatic images may be greater than the
overlap between consecutive color images.

[0008] This Summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the Detailed
Description. This Summary is not intended to identify key features or
essential features of the claimed subject matter, nor is it intended that
this Summary be used to limit the scope of the claimed subject matter.
Furthermore, the claimed subject matter is not limited to implementations
that solve any or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a schematic diagram showing aspects of a large format
digital camera having multiple optical systems and detector arrays
provided in one embodiment presented herein;

[0010] FIG. 2 is a schematic diagram showing the footprint of a primary
camera system overlaid with the footprint of a secondary camera system in
a large format digital camera presented in one embodiment disclosed
herein;

[0011] FIG. 3 is a perspective diagram showing a perspective view of the
footprint of a primary camera system and the footprint of a secondary
camera system in a large format digital camera presented in one
embodiment disclosed herein;

[0012] FIG. 4A is a schematic diagram illustrating the overlap between the
footprint of a sequence of consecutive images taken with a primary camera
system and the footprint of a sequence of consecutive images taken with a
secondary camera system in a large format digital camera presented one
embodiment disclosed herein;

[0013] FIG. 4B is a perspective diagram illustrating the overlap between
the footprint of a sequence of consecutive images taken on several flight
lines with a primary camera system and the footprint of a sequence of
consecutive images taken with a secondary camera system in a large format
digital camera presented one embodiment disclosed herein; and

[0014] FIG. 5 is a flow diagram showing one illustrative process presented
herein for the airborne optical registration of urban areas using a large
format digital camera having multiple optical systems and detector arrays
provided in one embodiment presented herein.

DETAILED DESCRIPTION

[0015] The following detailed description is directed to a large format
digital camera having multiple optical systems and detector arrays. In
the following detailed description, references are made to the
accompanying drawings that form a part hereof, and which are shown by way
of illustration specific embodiments or examples. Referring now to the
drawings, in which like numerals represent like elements throughout the
several figures, aspects of a large format digital camera having multiple
optical systems and detector arrays will be presented.

[0016] FIG. 1 is a schematic diagram showing aspects of a large format
digital camera 100 having multiple optical systems 106A-106B and detector
arrays 110A-110B provided in one embodiment presented herein. As shown in
FIG. 1, the large format digital camera 100 includes a primary camera
system 104A, which might be referred to herein as the first camera
system, and a secondary camera system 104B, which might be referred to
herein as the second camera system. Although FIG. 1 illustrates only one
secondary camera system 104B, it should be appreciated that other
embodiments might include multiple secondary camera systems 104B.

[0017] According to one embodiment, the primary camera system 104A
includes an optical system 106A that has a focal length 108A. The
secondary camera system 104B includes an optical system 106B that has a
focal length 108B that is longer than the focal length 108A of the
optical system 106A. In this manner, the secondary camera system 104B is
configured to produce images having a narrower field of view than images
produced by the primary camera system 104A. Images produced by the
primary camera system 104A have a wider field of view than images
produced by the secondary camera system 104B. The optical systems
106A-106B may include other conventional optical elements to produce a
suitable image at the desired focal length.

[0018] According to one implementation, the primary camera system 104A is
configured with an electro optical detector array 110A capable of
capturing panchromatic image data 112. As known in the art, a
panchromatic image sensor, such as the electro optical detector array
110A, is sensitive to all or most of the entire visible spectrum.
According to embodiments, the secondary camera system 104B is configured
with an electro optical detector array 110B capable of capturing color
image data 116. For instance, the secondary camera system 104B might be
equipped with a suitable charge coupled device ("CCD") array configured
for capturing the color image data 116. According to embodiments, the
camera system presented herein is a frame camera (also referred to as a
framing camera), as opposed to a camera that utilizes push-broom sensing.

[0019] It should be appreciated that the detector arrays 110A-110B
comprise arrays of individual electro-optical detectors, e.g.,
semiconductor devices that output an electric signal, the magnitude of
which is dependent on the intensity of light energy incident on such
electro-optical detector. Therefore, the signal from each electro-optical
detector in the arrays 110A-110B is indicative of light energy intensity
from a pixel area of the portion of the object or terrain being
photographed, and the signals from all of the individual electro-optical
detectors in the arrays 110A-110B are indicative of light energy
intensity from all of the pixel areas of the portion of the object or
terrain being photographed. Consequently, the signals from the
electro-optical detectors in each of the detector arrays 110A-110B,
together, are indicative of the pattern of light energy from the portion
of the object being photographed, so a sub-image of the portion of the
object can be produced from such signals. First, however, the signals are
amplified, digitized, processed, and stored, as is well known to those of
ordinary skill in the art.

[0020] The electro-optical detector arrays 110A-110B are connected
electrically by suitable conductors to a control circuit (not shown),
which includes at least a microprocessor, input/output circuitry, memory,
and a power supply for driving the electro-optical detector arrays
110A-110B, retrieving image data from of the arrays 110A-110B, and
storing the image data. Other data processing functions, for example
combining images and/or performing image display functions may be
accomplished within the large format digital camera 100 or by other
external data processing equipment.

[0021] According to implementations, the resolution of the electro optical
detector array 104B in the secondary camera system 104B is greater than
the resolution of the electro optical detector array 104A in the primary
camera system 104A. In this manner, the large format digital camera 110
can produce a panchromatic image file 114 from the primary camera system
104A using a wide-angle geometry that is suitable for use in a
photogrammetric workflow that includes image-based georeferencing and
digital surface modeling. The large format digital camera 110 can also
simultaneously produce a higher-resolution color image file from the
secondary camera system 104B using a narrow-angle geometry suitable for
use in a photogrammetric workflow that includes ortho image production.

[0022] As described briefly above, the primary camera system 104A and the
secondary camera system 104B might be mounted within a common housing
102. In this embodiment, a front glass plate 120 might be mounted within
the housing 102 to protect the optical systems 106A-106B. In alternate
implementations, the primary camera system 104A and the secondary camera
system 104B are mounted in separate housings (not shown). In both cases,
the primary camera system 104A, the secondary camera system 104B, and the
housing 102 are configured for mounting and use within an aircraft.

[0023] FIG. 2 is a schematic diagram showing the footprint 202 of the
primary camera system 104A overlaid with the footprint 204 of the
secondary camera system 104B in the large format digital camera 100
according in one embodiment disclosed herein. As illustrated in FIG. 2,
the primary camera system 104A and the secondary camera system 104B are
configured in one embodiment such that the large format digital camera
100 can produce overlapping images at two different image scales offering
two different footprints 202 and 204.

[0024] According to one embodiment, images produced by the primary camera
system 104A have a larger footprint 202 and are larger in size than those
produced by the secondary camera system 104B. Images produced by the
secondary camera system 104B have a smaller footprint 204 and are smaller
in size than those produced by the primary camera system 104A and offer a
higher resolution narrow angle color image.

[0025] As also illustrated in FIG. 2, the footprint 204 of the secondary
camera system 104B may be configured to cover the center of the footprint
202 of the primary camera system 104A. By overlapping the footprints 202
and 204 in the manner shown in FIG. 2, a portion of the images produced
by the primary camera system 104A can be enhanced by the images produced
by the secondary camera system 104B. FIG. 3 provides a perspective view
of the footprint 200 of the primary camera system 104A and the footprint
204 of the secondary camera system 104B when an image is taken from a
common point 302 by both camera systems 104A-104B.

[0026] FIG. 4A shows a top-down view that illustrates the overlap between
the footprint 200 of a sequence of consecutive images taken with the
primary camera system 104A and the footprint 204 of a sequence of
consecutive images taken with the secondary camera system 104B in the
large format digital camera 100 in one embodiment disclosed herein. As
discussed briefly above, the large format digital camera 100 may be
mounted and configured for use within an aircraft (not shown). When the
aircraft is flown according to a well-defined flight line 400A, the large
format digital camera 100 may be configured to capture a sequence of
images along the flight line 400A. FIG. 4A illustrates the footprints
202A-202D of a sequence of images taken using the primary camera system
104A and the footprints 204A-204D of a sequence of images taken using the
secondary camera system 104B along the flight line 400A.

[0027] As illustrated in FIG. 4A, the large format camera 100 may be
further configured such that the primary camera system 104A produces a
sequence of consecutive panchromatic images that have footprints
202A-202D wherein consecutive sequential images overlap one another. The
secondary camera system 104B may similarly be configured to produce a
sequence of consecutive color images that have footprints 204A-204D
wherein consecutive sequential images overlap one another and also
overlap the images produced by the primary camera system 104A. The
overlap between the footprints of consecutive panchromatic images may be
greater than the overlap between the footprints of consecutive color
images.

[0028] FIG. 4B is a perspective diagram illustrating the overlap between
the footprints 200 of a sequence of consecutive images taken on several
flight lines 400A-400B with the primary camera system 104A and the
footprints 204 of a sequence of consecutive images taken with a secondary
camera system 104B in the large format digital camera 100 in one
embodiment disclosed herein. If, as illustrated in FIG. 4B, images are
produced by the primary camera system 104A and the secondary camera
system 104B along multiple well-defined flight lines 400A-400B by means
of aerial photogrammetric image acquisition, the footprints 202 of the
primary camera system 104A overlap one another in the sequence of
exposures along the flight lines 400A-400B. The footprints 204 of the
secondary camera system 104B also overlap with the footprints 202 of the
primary camera system 104A and the footprint 204 of the secondary camera
system 104B.

[0029] Along the flight lines 400A-400B, images are therefore produced in
such a way that the sequence of images produced by the primary camera
system 104A and the images produced by the secondary camera system 104B
create continuous image strips of overlapping images. The flight lines
400A-400B may be defined in such a way that the large format digital
camera 100 captures images covering an entire project area.

[0030] According to various embodiments, image acquisition by the
secondary camera system 104B may be triggered substantially
simultaneously with image acquisition by the primary camera system 104A
and, accordingly, images from the secondary camera system 104B may be
acquired at the same position and with the same camera attitude as images
from the primary camera system 104A. Alternatively, the trigger for the
secondary camera system 104B may be independent from the primary camera
system 104A, e.g., may be at a higher rate than images captured by the
primary camera system. Either embodiment, as well as any combination
thereof, is contemplated to be within the scope of embodiments presented
herein.

[0031] When the primary camera system 104A and the secondary camera system
104B are triggered at the same time, the images produced by the secondary
camera system 104B may be registered to the images produced by the
primary camera system 104A using the same trigger event. Additionally,
images produced by the secondary camera system 104B may be calibrated to
images of the primary camera system 104A through the use of a precisely
surveyed and well-structured object (known as a "calibration object").

[0032] The images of the secondary camera system 104B may also be stitched
to the images of the primary camera system 104B using traditional
methods. Additionally, the images generated by the primary camera system
104A can be used to reconstruct the three dimensional form of an object
(for instance, the buildings of a city by means of a digital surface
model) and the images of the secondary camera system 104B, with a higher
geometric resolution, may be used to extract high resolution photo
texture which can then used for the production of urban ortho image maps.

[0033] Referring now to FIG. 5 additional details will be provided
regarding the embodiments presented herein for a large format digital
camera 100 having multiple optical systems and detector arrays. In
particular, FIG. 5 is a flow diagram showing a routine 500 that
illustrates one process presented herein for the airborne optical
registration of urban areas using the large format digital camera 100
described above.

[0034] The routine 500 begins at operation 502, where the large format
digital camera 100 is calibrated. As discussed above, the large format
digital camera 100 may be calibrated using a calibration object such that
the footprint of images produced by the secondary camera system 104B
overlap the central portion of the footprint of images produced by the
primary camera system 104A. As also discussed above, the large format
digital camera 100 may be installed in an aircraft and utilized to
capture ground images as the aircraft is flown along a well-defined
flight line. Such images may be captured and stored in an appropriate
digital storage device integrated with or external to the large format
digital camera 100.

[0035] From operation 502, the routine 500 proceeds to operation 504 where
panchromatic image files 114 are received from the primary camera system
104A. The routine then proceeds to operation 506, where color image files
118 are received from the secondary camera system 104B. Once the images
files have been received from both camera systems 104A-104B, the routine
500 proceeds to operation 508, where the image files 114 from the primary
camera system 104A are co-registered with the image files 118 from the
secondary camera system 104B.

[0036] From operation 508, the routine 500 proceeds to operation 510,
where the image files 114 from the primary camera system 104A are
utilized in a photogrammetric workflow that includes image-based
georeferencing and digital surface modeling. From operation 510, the
routine 500 proceeds to operation 512, where the image files 118 from the
secondary camera system 104B are utilized for ortho image production. The
routine 500 proceeds from operation 512 to operation 514, where it ends.

[0037] Based on the foregoing, it should be appreciated that a large
format digital camera 100 having multiple optical systems and detector
arrays has been disclosed herein that is suitable for use in the airborne
optical registration of urban areas. It should also be appreciated that
the subject matter described above is provided by way of illustration
only and should not be construed as limiting. Various modifications and
changes may be made to the subject matter described herein without
following the example embodiments and applications illustrated and
described, and without departing from the true spirit and scope of the
present invention, which is set forth in the following claims.

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